Study on the propagation characteristics of seismic waves perpendicular to the earth-rock dam axis

Geophones are typically arranged along the dam axis when seismic wave methods are used to detect latent hazards. Due to the complexity of the potential hazards and physical parameters inside the dam, the detection results may be inaccurate based on the seismic data in a single direction. The incorporation of seismic data perpendicular to the dam axis will effectively improve the detection accuracy. Mastering the propagation characteristics of seismic waves perpendicular to the earth-rock dam axis are necessitated for seismic data processing and interpretation yet remain a research gap, and the kinematic characteristics of various wave fields are underexplored. Here, an adaptive free boundary treatment scheme at the dam crest and slope is proposed based on the structural features of actual earth-rock dams, and the corresponding difference mode is provided. The full-wavefield simulation of seismic waves perpendicular to the dam axis is achieved using a finite-difference method with a spatial sixth-order and temporal second-order staggered grid. The kinematic characteristics of seismic wave propagation within the dam are elaborated. The layout of geophones perpendicular to the dam axis allows for recording the direct longitudinal wave and direct shear wave penetrating the dam, and surface wave reflection occurs at the crest corners and bottom corners. Influenced by the dam's slope structure, the path lengths of the reflected body waves vary irregularly depending on the locations of receiver points on the dam slope, resulting in irregular travel-time curves in seismic records.